There is disclosed herein a filter element, and in particular, a large surface area filter element for use in medical applications.
In many medical applications fluids, such as blood, intravenous solutions, etc., are filtered to remove undesirable filtratable constituents. In some applications, such as flood filtration, surface-type or depth-type filter media is used. Surface-type media is usually a web of open-mesh material which is held, by a frame, in a filtering position. Depth-type media is usually a pad of fibrous or porous material.
In blood administration sets, blood or plasma is conducted from a reservoir, usually a flexible plastic bag, through a drip chamber and then to the patient via a catheter. Such sets are sold by Travenol Laboratories, Inc., Deerfield, Ill., under product code numbers such as 2C2037 and 2C2157.
The drip chamber may include a filter element so that blood entering the chamber flows through the filter element and then exits the chamber. The drip chamber controls the delivery of fluid on a drop-by-drop basis.
In some constructions, the drip chamber includes a cylindrical housing, a cylindrical filter element that fits into the housing, and a cap that seals the chamber. The filter element includes an injection molded frame and a surface-type or depth-type filter media supported by the frame. The filter media has a generally cylindrical surface. The molding technique employs a split mold cavity and core which permits injection molding of the frame and attachment of the filter media in one step. This is sometimes referred to as overmolding.
It has been determined that in some applications, it is desirable to increase the filtering ability of the filter. However, it may be undesirable to increase the length or width of the filter as that would require changing the geometry (i.e., size and shape) of the drip chamber.
Pleating of a filter can increase the surface area, but pleated filters have not been made using molding techniques as pleated filters include undercuts or re-entrant angles that would preclude opening of the mold to remove the filter element without destruction of the element.
It is therefore an object of this invention to increase the filtering capacity of a medical filter element without changing the size and shape of the related housing.
It is another object of this invention to increase the filtering capacity of a medical filter element while still permitting the filter element to be manufactured by molding.
These and other objects of this invention will become apparent from the following description and appended claims.